PMID- 27378210
OWN - NLM
STAT- MEDLINE
DCOM- 20170217
LR  - 20181202
IS  - 2050-7895 (Electronic)
IS  - 2050-7887 (Linking)
VI  - 18
IP  - 8
DP  - 2016 Aug 10
TI  - Sticking to (first) principles: quantum molecular dynamics and Bayesian 
      probabilistic methods to simulate aquatic pollutant absorption spectra.
PG  - 1068-77
LID - 10.1039/c6em00233a [doi]
AB  - This work explores the relationship between theoretically predicted excitation 
      energies and experimental molar absorption spectra as they pertain to 
      environmental aquatic photochemistry. An overview of pertinent Quantum Chemical 
      descriptions of sunlight-driven electronic transitions in organic pollutants is 
      presented. Second, a combined molecular dynamics (MD), time-dependent density 
      functional theory (TD-DFT) analysis of the ultraviolet to visible (UV-Vis) 
      absorption spectra of six model organic compounds is presented alongside accurate 
      experimental data. The functional relationship between the experimentally 
      observed molar absorption spectrum and the discrete quantum transitions is 
      examined. A rigorous comparison of the accuracy of the theoretical transition 
      energies (DeltaES0-->Sn) and oscillator strength (fS0-->Sn) is afforded by the 
      probabilistic convolution and deconvolution procedure described. This method of 
      deconvolution of experimental spectra using a Gaussian Mixture Model combined 
      with Bayesian Information Criteria (BIC) to determine the mean (mu) and standard 
      deviation (sigma) as well as the number of observed singlet to singlet transition 
      energy state distributions. This procedure allows a direct comparison of the 
      one-electron (quantum) transitions that are the result of quantum chemical 
      calculations and the ensemble of non-adiabatic quantum states that produce the 
      macroscopic effect of a molar absorption spectrum. Poor agreement between the 
      vertical excitation energies produced from TD-DFT calculations with five 
      different functionals (CAM-B3LYP, PBE0, M06-2X, BP86, and LC-BLYP) suggest a 
      failure of the theory to capture the low energy, environmentally important, 
      electronic transitions in our model organic pollutants. However, the method of 
      explicit-solvation of the organic solute using the quantum Effective Fragment 
      Potential (EFP) in a density functional molecular dynamics trajectory simulation 
      shows promise as a robust model of the hydrated organic pollutant. Furthermore, 
      the described protocol can be extended using higher-level equilibration and 
      vertical excitation methods to increase the numerical accuracy and describe 
      multi-reference electronic transitions. Finally, a measure of the accuracy of 
      theoretically derived absorption spectra is discussed as a tool to further 
      develop our capacity to produce accurate a priori simulations of sunlight-driven 
      photochemistry in natural waters.
FAU - Trerayapiwat, Kasidet
AU  - Trerayapiwat K
AD  - Department of Chemistry, Bowdoin College, 6600 College Station, Brunswick, ME, 
      USA. seustis@bowdoin.edu.
FAU - Ricke, Nathan
AU  - Ricke N
AD  - Department of Chemistry, Bowdoin College, 6600 College Station, Brunswick, ME, 
      USA. seustis@bowdoin.edu.
FAU - Cohen, Peter
AU  - Cohen P
AD  - Department of Chemistry, Bowdoin College, 6600 College Station, Brunswick, ME, 
      USA. seustis@bowdoin.edu.
FAU - Poblete, Alex
AU  - Poblete A
AD  - Department of Chemistry, Bowdoin College, 6600 College Station, Brunswick, ME, 
      USA. seustis@bowdoin.edu.
FAU - Rudel, Holly
AU  - Rudel H
AD  - Department of Chemistry, Bowdoin College, 6600 College Station, Brunswick, ME, 
      USA. seustis@bowdoin.edu.
FAU - Eustis, Soren N
AU  - Eustis SN
AD  - Department of Chemistry, Bowdoin College, 6600 College Station, Brunswick, ME, 
      USA. seustis@bowdoin.edu.
LA  - eng
PT  - Journal Article
PL  - England
TA  - Environ Sci Process Impacts
JT  - Environmental science. Processes & impacts
JID - 101601576
RN  - 0 (Water Pollutants, Chemical)
RN  - 059QF0KO0R (Water)
SB  - IM
MH  - Bayes Theorem
MH  - *Molecular Dynamics Simulation
MH  - *Quantum Theory
MH  - Spectrophotometry, Ultraviolet
MH  - Water
MH  - Water Pollutants, Chemical/*chemistry
EDAT- 2016/07/06 06:00
MHDA- 2017/02/18 06:00
CRDT- 2016/07/06 06:00
PHST- 2016/07/06 06:00 [entrez]
PHST- 2016/07/06 06:00 [pubmed]
PHST- 2017/02/18 06:00 [medline]
AID - 10.1039/c6em00233a [doi]
PST - ppublish
SO  - Environ Sci Process Impacts. 2016 Aug 10;18(8):1068-77. doi: 10.1039/c6em00233a.